Diagnosis of urinary tract infections: need for a reflective rather than reflexive approach

Abstract

To the Editor-We read with great interest the study by Munigala et al 1 on the impact of changing urine testing orderables on the number and positivity of urine cultures. With the increased attention to catheter-associated urinary tract infection (CAUTI), the vast majority of hospitals in the United States have steered their attention to "stewardship of culturing" to reduce the detection of asymptomatic catheter-associated bacteriuria. In this retrospective study, the authors evaluate changing urine culture reflex testing in order sets and engaging clinicians regarding the change. Prior to the intervention, a urinalysis would be reflexed to culture if it included any protein, blood, nitrite, or leukocyte-esterase positive results. With the intervention, the urinalysis reflexed to culture only if it was positive for either nitrite or leukocyte esterase. A 45% reduction in urine cultures performed was observed after implementation, although catheter-associated bacteriuria and CAUTI rates did not significantly change.The main intervention was to exclude urinalysis parameters of proteinuria or blood, both elements not typically associated with bacteriuria, from reflexing to cultures. This raises the issue that there is no national standard for "reflex urine culture" criteria in hospitalized patients. 2 A previous study that incorporated reflex urine cultures relied on arbitrary triggers (white cells >10 per high-power field) of the urinalysis to reflex to culture, leading to a reduction in catheter-associated bacteriuria but not antibiotic use. 3 Other successful efforts to reduce culturing and CAUTI have focused on engaging clinicians with protocols on how to address fever without requiring strict implementation of urinalysis reflex to cultures. 4 Whether any of the interventions have improved the diagnosis of urinary tract infection (UTI) remains unknown.Notably, the reduction in urine cultures from Munigala's study were disproportionately related to catheterized patients compared to clean-catch samples (76% vs 38% decrease). This finding indicates a potential clinician bias toward ordering fewer cultures in catheterized patients during the intervention phase in a population that is more likely to develop bacteriuria and pyuria because of instrumentation and, thus, more likely to have abnormal urinalyses.Bacteriuria was common, with >25% of urine cultures being positive, identified as either >100,000 colony-forming units per milliliter (CFU/mL) for clean-catch collection or >10,000 CFU/ mL for catheterized patients. The extent of bacteriuria likely would have been even higher if cultures with lower colony counts were included. The number of positive cultures per 1,000 patient days decreased by more than one-third, but it is not clear whether the improvements were related to a general reduction in urine culturing compared to better identification of symptomatic patients. Although a negative urinalysis may have a high negative predictive value for bacteriuria and infection, an "abnormal" result does not indicate infe...

Quality Improvement Interventions and Implementation Strategies for Urine Culture Stewardship in the Acute Care Setting: Advances and Challenges

“…In addition, urine cultures and urinalyses are often included as pre-selected tests in many order sets (e.g., pre-operative, admission). Overtesting is especially relevant to urine cultures, where the positive predictive value is heavily influenced by symptoms and collection techniques [22].…”

Incidence and Diagnostic Yield of Repeat Urine Culture in Hospitalized Patients: an Opportunity for Diagnostic Stewardship

“…A similar intervention to indicate to physicians that a recent urine culture was ordered, is pending, or has been completed, along with the time and date, may lead to more discerning utilization practices. A thoughtful design of CPOE systems coupled with the implementation of diagnostic stewardship may play an important role in improving the cost-effectiveness and quality of clinical patient care (18)(19)(20).…”

Deconstructing the urinalysis: A novel approach to diagnostic and antimicrobial stewardship

“…39 Although reflex urine cultures have resulted in a reduction in urine culture orders in patients without pyuria, this practice should be avoided in asymptomatic patients or those not suspected to have a UTI. 40 Additionally, laboratories use different urinalysis parameters and cutoffs to proceed to culture, which leads to confusion and lack of standardized care. 36 To complicate matters, different forms of urinalysis orderables exist within the same hospital as well as across multiple laboratories without guidance related to pretest probability or underlying diagnosis (eg, urinalysis macroscopic with reflex to microscopic urinalysis, complete urinalysis, urinalysis with reflex to culture, and/or urinalysis dipstick).…”

“…41 Clinicians, however, will often seize this abnormal result and prematurely mislabel the patient with a diagnosis of UTI. 40 Optimizing the urinalysis Urinalysis and urine dipstick tests are easy and inexpensive screening tests, but their results can have important downstream consequences on urine cultures and antimicrobial prescribing. The level of pyuria on urinalysis correlates with increasing use of urine cultures and inappropriate antimicrobial prescribing.…”

“…However, reflex urine cultures have poor utility in catheterized patients, neonates, and neutropenic patients. 40 Clinicians should use the clinical context to develop a pretest probability for a likely diagnosis to which the urinalysis parameters should be applied. This process will allow the clinician to develop a differential diagnosis using the urinalysis parameters of significance while giving less weight to findings that are likely unrelated to the underlying kidney disease.…”